The present invention relates to a filter for purifying exhaust gas and the like which are discharged from an internal combustion engine of an automobile or the like.
Conventionally, a ceramic honeycomb structure carrying oxidizing catalyst has been employed for such purpose. When such a ceramic honeycomb structure carrying oxidizing catalyst is disposed within the exhaust gas system of the automobile, open passages of the honeycomb structure extend in the same direction as the flowing direction of the exhaust gas. Therefore, most of the exhaust gas flows through the open passages of the honeycomb structure in a straight line without impinging against the walls of the open passages. As a result, fine carbon particles contained within the exhaust gas are not sufficiently contacted with the oxidizing catalyst so that the exhaust gas purifying efficiency is low.
And also a porous ceramic body conventionally is used as a filter for purifying exhaust gas. Since open passages of this filter extend in various directions and the contact area with the exhaust gas is large, the purifying efficiency is high. But mechanical strength against vibrations or the like is remarkably inferior to that of the filter composed of the ceramic honeycomb structure.
Accordingly, one object of the present invention is to provide a filter for exhaust gas having excellent mechanical strength, and wherein fine particles within the exhaust gas will be filtered out with high efficiency.
Another object of the present invention is to provide a filter for purifying exhaust gas wherein a porous ceramic filtering material is integrally retained by a ceramic supporting member.
Still another object of the present invention is to provide a filter for purifying exhaust gas, which is suitable to catch and collect fine carbon particles contained within the exhaust gas of a diesel engine.